There are a number of things we think we know about Adam Lanza, the Newtown, Connecticut 20-year-old, who last Friday murdered his mother, then shot his way into Sandy Hook Elementary School and killed 20 first-graders and six adults before turning a gun on himself.

We’ve been told, by a former classmate, that he was “weird.” We’ve been told, by a family friend, that he played a lot of violent video games. And we’ve also been told by such sources that he had a “developmental disorder,” that some say was Asperger’s Syndrome.

From this, a narrative has emerged of a troubled young man, induced into violence by his preferred choice of media, and failed by an inadequate mental health system. This narrative has caught on so successfully that, as of Wednesday, a Gallup poll found far more Americans believing that events like the Newtown tragedy could be avoided through increased federal spending on mental health screening and services than by banning the sale of assault weapons.

And yet, in truth, we have virtually no hard facts to back up this storyline.

How often did Lanza play the most violent games? How did he feel about them? How did they affect him? Did they desensitize him to violence or provoke blood lust? We don’t know, and most likely never will.

Did he really have Asperger’s? Was he diagnosed with anything in addition to the “developmental disorder” — or was that just a palatable-sounding phrase his family and family friends used to avoid invoking scarier, more threatening terms like “mental illness”? We don’t know what lay behind the extremely inward-turned behavior his classmates saw, or the murderous violence that erupted last week. Was it extreme, toxic anxiety? Paranoia? Voices? Righteous rage? We may never know.

We don’t know that Lanza’s crime represents a failure of our “system” of mental health care in America, as has been said countless times this week, because we don’t know what, if any, mental health care he was receiving in recent years at all. Although a babysitter has said that Lanza took medication as a child, we don’t know what kind of medication it was. We don’t know what the Lanzas’ attitude toward mental health care was. Did Nancy, who homeschooled Adam for years, reject the mainstream beliefs of child psychiatry, as many in the home-schooling community do?

There are exactly two rock-solid, actionable facts in the Adam Lanza story. He lived in a home filled with firearms. And had he not had access to semi-automatic weapons, he would not have been able to take 26 lives in a matter of minutes. These facts are now being buried in an onslaught of supposition about the effects of video game violence and the need — which I otherwise entirely agree with — for more and better mental health care for America’s kids.

The incontrovertible facts of the Lanza case are, for now, what we as a nation should be focusing on as we come to terms with the Newtown tragedy. All the rest is just talk.